Channel driver circuit

ABSTRACT

A channel driver circuit includes a differential module and a driver module. In some examples, the channel driver circuit also includes a sigma-delta module. The differential module receives, via a single node of a load, a channel driving signal that is provided to the load at the single node (e.g., that is based on an electrical characteristic of the load) and generates an analog error signal that is based on the channel driving signal and a reference signal. The driver module is coupled to the differential module and generates the channel driving signal based on the analog error signal or a digital error signal corresponding to the analog error signal and transmits the channel driving signal via the single node to the load. The channel driver circuit simultaneously transmits the channel driving signal to the load at the single node and senses the channel driving signal at the single node.

CROSS REFERENCE TO RELATED PATENTS

The present U.S. Utility Patent Application claims priority pursuant to35 U.S.C. § 120 as a continuation of U.S. Utility application Ser. No.16/253,717, entitled “CHANNEL DRIVER CIRCUIT,” filed Jan. 22, 2019,pending, which claims priority pursuant to 35 U.S.C. § 119(e) to U.S.Provisional Application No. 62/620,812, entitled “CHANNEL DRIVERCIRCUIT,” filed Jan. 23, 2018, and U.S. Provisional Application No.62/630,595, entitled “ANALOG FRONT END CHANNEL DRIVER CIRCUIT,” filedFeb. 14, 2018, all of which are hereby incorporated herein by referencein their entirety and made part of the present U.S. Utility PatentApplication for all purposes.

U.S. Utility application Ser. No. 16/253,717 also claims prioritypursuant to 35 U.S.C. § 120, as a continuation-in-part (CIP) of U.S.Utility patent application Ser. No. 16/109,600, entitled “MULTI-TOUCHSENSOR AND ELECTROSTATIC PEN DIGITIZING SYSTEM UTILIZING SIMULTANEOUSFUNCTIONS FOR IMPROVED PERFORMANCE,” filed Aug. 22, 2018, pending, whichclaims priority pursuant to 35 U.S.C. § 120 as a continuation of U.S.Utility application Ser. No. 15/506,097, entitled “MULTI-TOUCH SENSORAND ELECTROSTATIC PEN DIGITIZING SYSTEM UTILIZING SIMULTANEOUS FUNCTIONSFOR IMPROVED PERFORMANCE,” filed Feb. 23, 2017, now issued as U.S. Pat.No. 10,120,498 on Nov. 6, 2018, which is a U.S. National StageApplication submitted pursuant to 35 U.S.C. § 371 of Patent CooperationTreaty Application No. PCT/US2016/038497, entitled “MULTI-TOUCH SENSORAND ELECTROSTATIC PEN DIGITIZING SYSTEM UTILIZING SIMULTANEOUS FUNCTIONSFOR IMPROVED PERFORMANCE,” filed Jun. 21, 2016, which claims prioritypursuant to 35 U.S.C. § 119(e) to U.S. Provisional Application No.62/183,062, entitled “MULTI-TOUCH SENSOR AND ELECTROSTATIC PENDIGITIZING SYSTEM UTILIZING SIMULTANEOUS FUNCTIONS FOR IMPROVEDPERFORMANCE,” filed Jun. 22, 2015, all of which are hereby incorporatedherein by reference in their entirety and made part of the present U.S.Utility Patent Application for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not Applicable.

BACKGROUND OF THE INVENTION Technical Field of the Invention

This invention relates generally to data communication systems and moreparticularly to sensed data collection and/or communication.

Description of Related Art

Sensors are used in a wide variety of applications ranging from in-homeautomation, to industrial systems, to health care, to transportation,and so on. For example, sensors are placed in bodies, automobiles,airplanes, boats, ships, trucks, motorcycles, cell phones, televisions,touch-screens, industrial plants, appliances, motors, checkout counters,etc. for the variety of applications.

In general, a sensor converts a physical quantity into an electrical oroptical signal. For example, a sensor converts a physical phenomenon,such as a biological condition, a chemical condition, an electriccondition, an electromagnetic condition, a temperature, a magneticcondition, mechanical motion (position, velocity, acceleration, force,pressure), an optical condition, and/or a radioactivity condition, intoan electrical signal.

A sensor includes a transducer, which functions to convert one form ofenergy (e.g., force) into another form of energy (e.g., electricalsignal). There are a variety of transducers to support the variousapplications of sensors. For example, a transducer is capacitor, apiezoelectric transducer, a piezoresistive transducer, a thermaltransducer, a thermal-couple, a photoconductive transducer such as aphotoresistor, a photodiode, and/or phototransistor.

A sensor circuit is coupled to a sensor to provide the sensor with powerand to receive the signal representing the physical phenomenon from thesensor. The sensor circuit includes at least three electricalconnections to the sensor: one for a power supply; another for a commonvoltage reference (e.g., ground); and a third for receiving the signalrepresenting the physical phenomenon. The signal representing thephysical phenomenon will vary from the power supply voltage to ground asthe physical phenomenon changes from one extreme to another (for therange of sensing the physical phenomenon).

The sensor circuits provide the received sensor signals to one or morecomputing devices for processing. A computing device is known tocommunicate data, process data, and/or store data. The computing devicemay be a cellular phone, a laptop, a tablet, a personal computer (PC), awork station, a video game device, a server, and/or a data center thatsupport millions of web searches, stock trades, or on-line purchasesevery hour.

The computing device processes the sensor signals for a variety ofapplications. For example, the computing device processes sensor signalsto determine temperatures of a variety of items in a refrigerated truckduring transit. As another example, the computing device processes thesensor signals to determine a touch on a touch screen. As yet anotherexample, the computing device processes the sensor signals to determinevarious data points in a production line of a product.

Touchscreen devices correspond to another possible environment in whichone or more sensors may be implemented. In certain touchscreen systems,projected capacitive touch sensors typically include a substrate uponwhich electrodes are disposed for sensing touch and a touch location.The substrate may be a durable glass having high optical transparencyfor viewing images displayed by an underlying display device thatdisplays images such as graphical buttons and icons. When a user touchesthe device on the outer surface of the substrate at a locationcorresponding to a desired selection displayed on the display device(e.g., with a finger or a stylus), the location is determined by thedevice sensing changes in capacitances to and between the electrodes.

In some projected capacitive touch sensors, the electrodes are arrangedin rows of electrodes and columns of electrodes. The rows and columnsare typically electrically isolated from one another via an insulatinglayer. A touch location is determined by driving electrodes of a firstorientation (e.g., the column electrodes or drive electrodes) with asquare wave signal (i.e., drive pulse). Sense circuitry coupled to theelectrodes of the other orientation (e.g., the horizontal electrodes orsense electrodes) measures current flow between the electrodes due tomutual capacitive coupling that exists between the column electrodes andthe row electrodes. The amount of current flow is directly proportionalto the value of the mutual capacitance and therefore facilitates thedetermination of the mutual capacitance. The mutual capacitance betweenthe intersection of a column electrode and a row electrode will changewhen a user touches the substrate in the vicinity of the intersection.

Typically, sense circuits for measuring the mutual capacitance operateby repetitively switching the sense electrodes to an input of an analogintegrator circuit, which includes an amplifier with a feedback circuitthat includes a capacitor that couples the amplifier output to theamplifier input. Such a circuit typically includes a switch that couplesthe input of the integrator to the sense electrode just before eachfalling edge of the drive pulse that drives the drive electrodes andthen uncouples just before each rising edge so as to integrate onlysignals of one polarity. The output of the integrator is then digitizedand the digitized value is utilized to determine whether and where atouch has occurred.

However, the relative magnitudes of parasitic capacitances of the switchat the input of the integrator are large in comparison with the mutualcapacitances between electrodes, which are typically measured infractions of a pico-farad. To overcome the adverse effects caused by theparasitic capacitances, a number of integration cycles may be performedbefore a touch location may accurately be determined. For example, theintegrator may integrate the signal measured on the sense electrode overtwo hundred or more cycles, which could take 1 millisecond (ms) or morefor a drive pulse with a frequency of 200 kilohertz (kHz). The length oftime to make a determination increases with the number of electrodesthat must be measured, which may adversely affect user experience forrelatively large displays that typically have a large number ofelectrodes to measure, relative to smaller projected capacitive (pCap)displays used in mobile devices.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a channel drivercircuit in accordance with the present invention;

FIG. 2A is a schematic block diagram of an embodiment of a differentialmodule in accordance with the present invention;

FIG. 2B is a schematic block diagram of another embodiment of adifferential module in accordance with the present invention;

FIG. 2C is a schematic block diagram of another embodiment of adifferential module in accordance with the present invention;

FIG. 2D is a schematic block diagram of another embodiment of adifferential module in accordance with the present invention;

FIG. 3A is a schematic block diagram of an embodiment of a sigma-deltamodule (e.g., which may be implemented as an analog to digital converter(ADC)) in accordance with the present invention;

FIG. 3B is a schematic block diagram of another embodiment of asigma-delta module (e.g., which may be implemented as an ADC) inaccordance with the present invention;

FIG. 3C is a schematic block diagram of another embodiment of asigma-delta module (e.g., which may be implemented as an ADC) inaccordance with the present invention;

FIG. 3D is a schematic block diagram of another embodiment of asigma-delta module (e.g., which may be implemented as an ADC) inaccordance with the present invention;

FIG. 3E is a schematic block diagram of another embodiment of asigma-delta module (e.g., which may be implemented as an ADC) inaccordance with the present invention;

FIG. 4A is a schematic block diagram of an embodiment of a driver module(e.g., which may be implemented as a digital to analog converter (DAC))in accordance with the present invention;

FIG. 4B is a schematic block diagram of an embodiment of a driver module(e.g., which may be implemented as a DAC) in accordance with the presentinvention;

FIG. 4C is a schematic block diagram of another embodiment of a drivermodule (e.g., which may be implemented as a DAC) in accordance with thepresent invention;

FIG. 5 is a schematic block diagram of an embodiment of a 2^(nd) orderchannel driver circuit in accordance with the present invention;

FIG. 6 is a schematic block diagram of an embodiment of a pulsemodulator circuit in accordance with the present invention;

FIG. 7 is a schematic block diagram of an embodiment of an Analog FrontEnd (AFE) channel driver circuit in accordance with the presentinvention;

FIG. 8A is a schematic block diagram of another embodiment of adifferential module in accordance with the present invention;

FIG. 8B is a schematic block diagram of another embodiment of adifferential module in accordance with the present invention;

FIG. 8C is a schematic block diagram of another embodiment of adifferential module in accordance with the present invention;

FIG. 9A is a schematic block diagram of another embodiment of a drivermodule (e.g., which may be implemented as a DAC) in accordance with thepresent invention;

FIG. 9B is a schematic block diagram of another embodiment of a drivermodule (e.g., which may be implemented as a DAC) in accordance with thepresent invention;

FIG. 10 is a schematic block diagram of an embodiment of an AFE channeldriver circuit coupled to a 1^(st) order sigma-delta (SD) module inaccordance with the present invention;

FIG. 11 is a schematic block diagram of an embodiment of an AFE channeldriver circuit with DSP, computing system (e.g., one or more computingdevices and/or processing circuitry), and multi-channel load interactionin accordance with the present invention;

FIG. 12 is a schematic block diagram of another embodiment of an AFEchannel driver circuit in accordance with the present invention;

FIG. 13 is a schematic block diagram of another embodiment of an AFEchannel driver circuit in accordance with the present invention;

FIG. 14 is a schematic block diagram of embodiment of an AFE channeldriver circuit with voltage level translation in accordance with thepresent invention;

FIG. 15 is a schematic block diagram of embodiment of an AFE channeldriver circuit operating with a low power triangle wave signal inaccordance with the present invention;

FIG. 16 is a schematic block diagram of an embodiment of a method forexecution by one or more devices in accordance with the presentinvention; and

FIG. 17 is a schematic block diagram of another embodiment of a methodfor execution by one or more devices in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present disclosure describes various aspects, embodiments, and/orexamples of the invention (and/or their equivalents) of a channel drivercircuit and related and associated circuitry, components, etc. such asmay be used in accordance with any of a variety of applicationsincluding sensor applications, transducer applications, etc. Forexample, a channel driver circuit is implemented to employ a referencesignal (e.g., such as may be provided from any circuitry, circuit,processing circuitry, component, device, etc. and may be in any of avariety of forms including an analog signal, a digital signal, etc.) andemploy that reference signal to generate a low impedance virtual versionof that reference signal that is driven onto, transmitted into, etc. aload (e.g., an external impedance network, a sensor, a transducer, anelectrode of a touchscreen system, etc. and/or any desired electricalload) while simultaneously receiving and outputting the load-modifiedsignal that is received from the load.

Note that the channel driver circuit is operative to detect any changesto the signal that is driven, transmitted, etc. to the load. Forexample, with respect to any signal that is driven and simultaneouslydetected by a channel driver circuit, note that any additional signalthat is coupled into a line, an electrode, a touch sensor, a bus, acommunication link, an electrical coupling or connection, etc.associated with that channel driver circuit is also detectable by thechannel driver circuit. For example, a channel driver circuit that isassociated with such a line, an electrode, a touch sensor, a bus, acommunication link, an electrical coupling or connection, etc. isconfigured to detect any signal from one or more other lines,electrodes, a touch sensors, a buses, a communication links, electricalcouplings or connections, etc. that get coupled into that line,electrode, touch sensor, bus, communication link, electrical coupling orconnection, etc. Generally speaking, any change to the signal that isdriven, transmitted, etc. to the load (e.g., such as based on anelectrical characteristic or a change of an electrical characteristic ofthe load such as due to the load itself, modification to the load,and/or any one or more externally injected signals) may be sensed,detected, etc. by the channel driver circuit).

The channel driver circuit operates by providing functionality includinglow impedance transmitting with a high impedance receiving while theexternal transmitting source signal effectively sees a ground terminatedload. In some examples, the channel drive circuit is configured tosubtract the reference signal and output only the load-affected signalinformation (e.g., as driven and/or as received).

In some examples, certain characteristics of a channel driver circuitmay be implemented to operate as a DAC to output signals and an ADC toprocess at the channel signal properties while offering low outputimpedance and high input impedance to received signals at the analogchannel node (e.g., where the channel driver circuit couples and/orconnects to the load) while shaping the noise (e.g., moving noise fromthe pass band portion of the signal range to a different frequencyspectrum of the signal, such as to a higher frequency range) at theanalog channel node and digital output node. In some examples, a channeldriver circuit is implemented to generate a digital output signal andalso has the ability to incorporate these analog driving, measuring,sensing properties with noise shaping properties.

Generally speaking, noise shaping may be viewed as moving noise from afrequency region of interest (e.g., “the pass band” portion of thesignal range) to a different frequency portion of the signal spectrum(e.g., oftentimes located at a higher frequency range). This may beachieved using oversampling and error integration such that the, whereit can be removed through filtering practices thus lowering the noisefloor. In some examples, a first order noise shaping effectivelyprovides a slope of minus 20 dB per decade of noise reduction as oneapproaches the signal of interest, for example. A second order would beminus 40 dB per decade and so on to higher orders, for example. Thegeneral starting point of the slope is dependent on many factors such asthe oversampling ration and the resolution of the analog to digitalconverter.

FIG. 1 is a schematic block diagram of an embodiment 100 of a channeldriver circuit in accordance with the present invention. The channeldriver circuit includes a differential module 101 coupled to asigma-delta (SD) module 102. In some examples, note that the SD module102 may be implemented as an analog to digital converter (ADC), an ADCmodule, ADC circuitry, etc. Note that the differential module 101 may beimplemented as a differential amplifier that is configured to receive asignal reference (SIG (ref)) at one input. The channel driver circuitfurther includes a driver module 103 that forms an outer loop feedbackfrom the output of the SD module 103 at a digital output node 106 to thedifferential module 101. In some examples, note that the driver module103 may be implemented as a digital to analog converter (DAC), a DACmodule, DAC circuitry, etc.

In some examples, the driver module 103 is configured to provide avariable power output to a channel input/output (IO) node 104 (e.g., viaa channel I/O interface) to drive an analog signal at a desired currentor voltage to a load 105. In some examples, note that the channel I/Onode 104 is a single node, a single line, a single-ended line, etc. Notethat the load 105 may be of any of a variety of types of electricalloads including an electrode of a touchscreen, a sensor, a transducer, adevice, an integrated circuit, circuitry, a computer, a tablet, a smartphone, an appliance, a motor, etc. and/or any other type of electricalload. The driver module 103 receives a digital error signal from the SDmodule 102 and reconstructs the error signal into an analog formatsubstantially similar to SIG (ref), this reconstructed signal is avirtualized version of the SIG (ref) signal (SIG (virt)).

In some examples, the digital error can have 1-to-M number of bits,where M is an integer ≥2. Thus, the channel driver circuit has an analogI/O at the channel I/O node 104 and a digital output at the digitaloutput node 106. In operation, the SD module 102 performs ananalog-to-digital conversion and the driver module 103 performs adigital-to-analog conversion. The differential module 101 creates ananalog error signal from the difference between the SIG (ref) and theSIG (virt) signals. The analog error signal is passed to the SD module102.

In some examples, the differential module 101 and the SD module 102 areconfigured to operate as a digital op-amp with input and feedbackimpedance networks. This implementation facilitates controllableimpedance, gain, current-to-voltage function, a channel driving signal,and voltage following. Further, the merging of function of DAC, digitalop-amp, ADC feedback and I/O impedance allows for gain differences atdifferent frequency ranges. In various embodiments, a self-capacitivemode of a touch screen device has a low gain requirement as it has alarge signal response, a mutual-capacitive mode transmit of a touchscreen device has low gain requirement as it is not usually demodulated(the change measured to see mutual from transmit row to row), and amutual-capacitive mode receive of a touchscreen device has a higher gainrequirement for the mutual frequency band or receive (the changemeasured on the receive line column) and the receiving channel may nothave to transmit large signals allowing headroom for increased gain.

The channel I/O node 104 is a node coupled to the driver module 103, aninput of the differential module 101, and the load 105. The load 105 canbe an analog device, such as any device or circuit capable of receivingand/or transmitting an analog signal to the channel driver circuit, oran impedance network where changes to the network impedance are to bemeasured. For example, the analog device may be a touchscreen or atouchscreen screen interface network circuit, which is an impedancenetwork typically formed of resistances and capacitances, where ananalog signal is driven to the touch screen and a returning analogsignal or change to the driven signal can indicate whether a touch eventhas occurred. The channel driver circuit can also be used inapplications with zero resistance sensors (wires), high frequency (HF)sensing using channel driver frequency greater than 1 megahertz (MHz)for the transmission and reception of HF signals using modulatingsigma-delta, a spectrum analyzer, or as a network analyzer.

The signal present at the channel I/O node 104 may be referred to as achannel driving signal or SIG (virt). This signal is driven by thesystem to act as a virtual version of SIG (ref). In some examples, thechannel driving signal includes the analog output signal SIG (virt)generated by the driver module 103 onto the load 105 and any signalsourced from the load 105 will be zeroed as a signal into a virtualground.

In some examples, the differential amplifier in the differential module101 has a first input port coupled to the channel I/O node 104 and asecond input node receiving a reference signal SIG (ref). SIG (ref) is areference signal desired to be output to the load 105 after beingprocessed by the channel driver circuit. The differential module 101compares and amplifies the difference between SIG (ref) and the SIG(virt) in order to generate an analog error signal. The analog errorsignal from the differential module 101 is then provided to an input ofthe SD module 102.

The differential module 101 can be implemented in a variety of ways. Forexample, different implementations may be used and selected based on anynumber of considerations including desiredperformance/attributes/characteristics.

In an example of operation and implementation, a channel driver circuitincludes a differential module (e.g., such as differential module 101),a driver module (e.g., such as driver module 103), and a sigma-deltamodule (e.g., such as SD module 102). The differential module isconfigured to receive a reference signal. The differential module isalso configured to receive, via a single node of a load, a channeldriving signal that is provided to the load at the single node. Thedifferential module is also configured to generate an analog errorsignal that is based on the channel driving signal and the referencesignal. Note that the channel driving signal is based on an electricalcharacteristic of the load, and

The driver module is coupled to the differential module and configuredto generate the channel driving signal based on a digital error signalcorresponding to the analog error signal. The driver module is alsoconfigured to transmit the channel driving signal via the single node tothe load. Note that the driver module includes a voltage to currentconverter circuitry configured to generate the channel driving signalbased on the digital error signal corresponding to the analog errorsignal.

The sigma-delta module is coupled to the differential module andconfigured to receive the analog error signal. The sigma-delta module isalso configured to process the analog error signal to generate thedigital error signal corresponding to the analog error signal. Thesigma-delta module is also configured to transmit the digital errorsignal corresponding to the analog error signal to a computing deviceand/or processing circuitry to be processed in accordance withinterpreting the digital error signal corresponding to the analog errorsignal. note that the channel driver circuit is configuredsimultaneously to transmit the channel driving signal to the load at thesingle node and to sense the channel driving signal at the single node.

In some examples, the differential module includes a differentialamplifier having a first input port configured to receive the channeldriving signal, a second input port configured to receive the referencesignal, and an output port configured to output the analog error signal.Also, the sigma-delta module includes an analog to digital converter(ADC) configured to process the analog error signal to generate thedigital error signal corresponding to the analog error signal. Inaddition, the driver module includes a digital to analog converter (DAC)configured to generate the channel driving signal based on the digitalerror signal corresponding to the analog error signal.

In other examples, the sigma-delta module includes a comparatorconfigured to receive the analog error signal and to process the analogerror signal to generate the digital error signal corresponding to theanalog error signal. The sigma-delta module also includes a flip-flopcircuit configured to store the digital error signal at leasttemporarily before transmitting the digital error signal correspondingto the analog error signal to the computing device and/or the processingcircuitry to be processed in accordance with interpreting the digitalerror signal.

In addition, in other examples, the differential module includes adifferential amplifier having a first input port configured to receivethe channel driving signal, a second input port configured to receivethe reference signal via a resistor, and an output port that is coupledto the second input port via another resistor and/or a capacitor and isconfigured to output the analog error signal. Note that the analog errorsignal is output from the differential amplifier as a single-endedanalog error signal or a differential analog error signal.

Note that the load may be of any of a variety of types including any oneor more of an electrode of a touchscreen, a sensor, a transducer, adevice, an integrated circuit, circuitry, a computer, a tablet, a smartphone, an appliance, or a motor.

FIGS. 2A-2D illustrate examples of possible embodiments of thedifferential module 101. Each of the embodiments shown in FIGS. 2A-2Dillustrate different respective implementations of a differential moduleincluding a differential amplifier configured to receive a first inputsignal at a first input port 202 and a second input signal at a secondinput port 203, and generate an analog error signal at output 204.

FIG. 2A is a schematic block diagram of an embodiment 201-1 of adifferential module in accordance with the present invention. Thisdiagram illustrates the differential amplifier 201 generating a singleended analog error signal at the output 204.

FIG. 2B is a schematic block diagram of another embodiment 201-2 of adifferential module in accordance with the present invention. Thisdiagram illustrates the differential amplifier 201 generating adifferential analog error signal at the output 204.

FIG. 2C is a schematic block diagram of another embodiment 201-3 of adifferential module in accordance with the present invention. Thisdiagram illustrates the differential amplifier 201 further including acapacitor C implemented to operate as an integrator and coupled betweenthe output 204 and the second input port 203.

FIG. 2D is a schematic block diagram of another embodiment 201-4 of adifferential module in accordance with the present invention. Thisdiagram illustrates the differential amplifier 201 further including aresistor 206 acting as a gain setting feedback and coupled between theoutput 204 and the first input port 202.

In the embodiments illustrated in FIGS. 2A-2D, the negative terminal ofthe differential amplifier can be configured to receive SIG (ref) andthe positive terminal of the differential amplifier can be configured toreceive the channel driving signal SIG (virt). Conversely, the positiveterminal of the differential amplifier can be configured to receive thechannel driving signal SIG (ref) and the negative terminal of thedifferential amplifier can be configured to receive SIG (ref), wherecorrecting inversion can be accomplished in other analog or digitalparts of the circuit. The differential module 101 may include one ormore inverters to invert various signals as needed in a particularimplementation. In alternative embodiments, the differential module 101is implemented to include a combination of circuit functions asdescribed herein or their equivalents.

FIG. 3A is a schematic block diagram of an embodiment of a sigma-deltamodule (e.g., which may be implemented as an analog to digital converter(ADC)) in accordance with the present invention. In some examples, an SDmodule such as described herein is implemented using sigma-deltamodulation techniques. In various embodiments and with reference to FIG.3A, the SD module 302-1 can include a 1-bit ADC with latch including acomparator 301 and a flip-flop circuit 302. The flip-flop circuit 302stores the 1-bit output from the comparator 301. The comparator convertsthe analog error signal into a digital error signal that is provided tothe driver module 103 and also provided as a digital output signal atthe digital output node 106 of the channel driver circuit. The digitalerror digital error signal can be further processed to determine thespectral content of the channel drive signal SIG (virt). The channeldriver circuit in this configuration produces first order noise shaping.Furthermore, the SD module 302-1 can be implemented as a multi-bit ADC.

FIG. 3B is a schematic block diagram of another embodiment of asigma-delta module (e.g., which may be implemented as an ADC) inaccordance with the present invention. FIG. 3B illustrates SD module302-2 including a multi-bit ADC including multiple comparators 301 ₁,301 ₂ . . . 301 _(N) coupled to an encoder 303. The encoder 303 receivessignals 1-N from the multiple comparators 301 ₁, 301 ₂ . . . 301 _(N)and provides multiple digital output signals 306 ₁, 306 ₂ . . . 306 _(N)at the digital output node.

FIG. 3C is a schematic block diagram of another embodiment of asigma-delta module (e.g., which may be implemented as an ADC) inaccordance with the present invention.

FIG. 3C illustrates a 1^(st) order SD module yielding a 2^(nd) ordercircuit, where the SD module 302-2 includes a differential amplifier304, a capacitor C, a comparator 301, a flip-flop circuit 302, and aswitch 306. The capacitor 305 is implemented to operate as an integratorcoupled between an input and the output of the differential amplifier304. Further, the differential amplifier 304 provides a modulated analogerror signal to the comparator 301.

In this implementation, the comparator 301 and flip-flop circuit 302forms a 1-bit ADC with latch, with the flip-flop circuit 302 storing the1-bit output from the comparator 301. The 1-bit output forms a digitalsignal as an output signal, which also controls the switch 306. Thecomparator 301 is configured to compare the modulated error signal ofthe differential amplifier 304 and a reference signal to generate adigital error signal. If the analog error signal has increased incomparison to a reference signal (e.g., shown as signal ground in FIG.3C), the comparator 301 generates a one (“1”). If the analog errorsignal has decreased, the comparator 301 generates a zero (“0”). Assuch, the SD ADC is configured to transmit the changes in, or thegradient of, the analog error signal. The flip-flop circuit 302 storesthe 1-bit output from the comparator 301. The 1-bit output forms adigital shaped noise spectrum waveform as an output signal, which alsocontrols the switch 306. The switch (e.g., which may be implemented as afeedback DAC) controls whether the high or low reference voltage isconnected to the second input of the amplifier 304. The switch 306 isconnected to the high reference voltage when the flip-flop circuit 302has a one (“1”) value and is connected to the low reference voltage whenthe flip-flop circuit 302 has a zero (“0”) value, or vice versa. Thehigh or low level is subtracted from the incoming signal to theamplifier 304 from a differential module, and the difference isintegrated on capacitor C thus the SD module 302-2 is configured totrack the average error and converts the incoming signal into a digitalpulse stream.

FIG. 3D is a schematic block diagram of another embodiment of asigma-delta module (e.g., which may be implemented as an ADC) inaccordance with the present invention.

FIGS. 3D-3E show multi-order SD modules, where an M order module yieldsan M+1 shaping order when integrated into a channel driver circuit(e.g., such as may be implemented in accordance with FIG. 1). FIG. 3Dillustrates a SD module including a cascade of integrators 310 withfeedforward summation (CIFF) coupled to an ADC 311, with a DAC 312 in afeedback connection.

FIG. 3E is a schematic block diagram of another embodiment of asigma-delta module (e.g., which may be implemented as an ADC) inaccordance with the present invention.

Similarly, FIG. 3E illustrates a SD module including a cascade ofintegrators 313 with distributed feedback (CIFB) coupled to an ADC 314,with a DAC 315 in a feedback connection.

In some examples, an SD module may be implemented to include one or moreintegrators located before a comparator (e.g., one or more integrators310 located before a comparator 301 such as in certain of the priordiagrams). For example, consider the comparator 301 being coupled to anoutput of an integrator, where the comparator 301 compares a modulatederror signal of the integrator and a reference signal to generate anoutput error signal.

If the analog error signal has increased in comparison to referencesignal (ground as shown in FIGS. 3D-3E), then the comparator 301generates a one (“1”). If the analog error signal has decreased, thecomparator 301 generates a zero (“0”). As such, the SD module isconfigured to transmit the changes in, or the gradient of, the analogerror signal. The integrator acts as a low pass filter (LPF) and shapesthe noise in the analog error signal so that the noise may be filteredoff. The integrator can be configured to perform forced modulation(e.g., noise shaping) of the amplified error signal to move noise fromlow to high frequencies of the error signal and generate the modulatederror signal. The SD module may include multiple integrators, which maybe implemented for a higher order circuit and better signal-to-noiseratios (SNR), though additional integrators may cause stability issuesin the channel driver circuit.

FIG. 4A is a schematic block diagram of an embodiment of a driver module(e.g., which may be implemented as a digital to analog converter (DAC))in accordance with the present invention. In some examples, a drivermodule 403 is implementation to include a current driver or a voltagedriver. In some examples, the driver module 403 includes avoltage-to-current (V/I) converter 401. The V/I converter 401 iscontrolled based on a current setting value.

In an example of operation and implementation, the current setting valueis set during a start-up of the channel driver circuit. The V/Iconverter 401 receives a digital pulsed signal with shaped noise andconverts the signal into a pulsed current analog signal with filteringoccurring on the load 405 with residual shaped noise remaining at 404depending on the output impedance of the V/I and the amount of externalcapacitance, as shown in FIG. 4A. The digital pulsed signal with shapednoise may be received from the digital output node 406, and the analogsignal with noise provided to the channel I/O node 404.

FIG. 4B is a schematic block diagram of an embodiment of a driver module(e.g., which may be implemented as a DAC) in accordance with the presentinvention. In this diagram, a driver module 403-1 is implemented toinclude a filter 402 at the output and coupled to the channel I/O node404-1. The V/I converter receives a digital pulsed signal then thefilter 402 smooths and provides a filtered analog signal to the channelI/O node 404-1 and to load 405-1. The digital pulsed signal with shapednoise may be received from the digital output node 406-1, and the analogsignal with noise provided to the channel I/O node 404-1 and to load405-1.

FIG. 4C is a schematic block diagram of another embodiment of a drivermodule (e.g., which may be implemented as a DAC) in accordance with thepresent invention. In this diagram, a driver module 403-2 is implementedto include filter 402 at the input and coupled to the digital outputnode 406-2 and precede the V/I converter 401, as shown in FIG. 4C. Thefilter 402 receives a digital pulsed signal with shaped noise andremoves the unwanted higher frequency components (e.g., such as when thefilter 402 is implemented as a LPF). The filtered signal is then passedto the V/I converter 401, which provides a varying current analog signalto the channel I/O node 404-2 and to the load 405-2.

Functionally, the driver module 403, 403-2, or 403-2 is configured toreceive the digital signal from a SD module and pushes out the channeldriving signal to the channel I/O node 404, 404-1, or 404-2. The channeldriving signal may be a sine wave with shaped noise, with the shapednoise filtered by filter 402 (e.g., which may be implemented as a LPF).Further, the V/I converter 401 can be configured to generate a channeldriving signal with a high impedance level. For example, the channeldriving signal may have an impedance of 50 kilo-ohms (kΩ). In someexamples, the filter 402 is implemented as a LPF configured to filterout noise signals when the SD module is a 2^(nd) or 3^(rd) ordersigma-delta module. The outer loop delta modulation may be augmented inthis scheme with a multiple orders of sigma-delta front end, via the SDmodule, to gain the benefits of the latest advancements in sigma-deltatechnology in noise shaping and resolution at the expense of increasingthe complex analog circuit usage.

Note that the alternative various implementations of channel drivercircuits with various implementations of a differential module, a SDmodule, and a driver module may be made.

FIG. 5 is a schematic block diagram of an embodiment of a 2^(nd) orderchannel driver circuit in accordance with the present invention. In thisdiagram, a 2^(nd) order channel driver circuit 500 is shown. The channeldriver circuit 500 includes the differential module 101, the SD module,and the driver module 103. The differential module 501 includes adifferential amplifier 501 coupled to the SD module, where thedifferential amplifier 511 is configured to receive a reference signalSIG (ref) at one input. The differential module 501 also includes anintegrator 502 coupled to the output of the differential amplifier 501and an input of the differential amplifier 501 that receives thereference signal SIG (ref). The driver module 503 that forms an outerloop feedback channel from the output of the SD module at a digitaloutput node to the differential module 501. The SD module may include a1^(st) order SD module (e.g., such as described with reference to FIG.3C). Alternative implementations of SD modules may be implemented. Insome examples, the driver module 503 is configured to provide a variablepower output to a channel I/O node 504 to drive the channel drivingsignal at a desired current or voltage to the load 105. In this example,the driver module 103 has a low pass converter based on a V/I converter505 followed by a capacitor 506.

The channel driver circuit 500 of FIG. 5 illustrates a 2^(nd) ordersigma-delta design. The circuit has higher order noise shapingcapabilities with fewer components in comparison to other designs. In anexemplary embodiment, channel driver circuit 500 is implemented on afield programmable gate array (FPGA) and operates with continuous-timesigma-delta modulation.

In some examples, a channel driver circuit may be configured forconcurrent modality of providing signals at one or more frequencies toan analog I/O via channel I/O node and monitoring the response of thedriven signals and simultaneously receiving one or more externallygenerated signal frequencies. The channel driver circuit uses continuouscoherent sampling while driving and simultaneously receiving multiplewaveforms to the analog device allowing for advanced signal processingmethods of the channel out digital data. Further, in certainapplications such as a touchscreen operation, the channel driver circuitis configured for parallel communicating transmit/receive signals formutual capacitance operation with one or more rows transmitting (using adifferent frequency per line) continuously and all columns receivingcontinuously (or vice versa).

A channel driver circuit (e.g., such as channel driver circuits 100,500) can be implemented using FPGA or an ASIC. In accordance withvarious embodiments, a channel driver circuit is capable of targetedsigma-delta noise shaping notching. The noise factor is shaped to asmall range, such as 25 kHz to 125 kHz to improve the noise floorcompared to a typical range of 0 to 200 kHz.

In various embodiments, a channel driver circuit includes feedbackimpedance network and I/O impedance networks resistive components withvariable or switched capacitor current shuttles with controllablefrequency and duty cycle. The variable impedance allows changes to gain(inverting and non-inverting gain of the digital op-amp) and driveimpedance. Further, a switched power supply (with frequency and dutycycle control) or switched capacitor charge pump is coupled to thedriver module 103 on the feedback loop such that high voltage can beused to increase voltage overhead necessary due to gain on the digitalop-amp or to increase the output signal driven onto the analog device.In some embodiments, the rails of the differential amplifiers,comparator, and switches will also have high voltage rails. When thechannel driver circuit is an M^(th) order circuit, the driver modulereconstruction filter and SIG (ref) reconstruction filter can be M−1order filters or higher. In various embodiments, the differential modulecan be replaced with a differential amplifier having good power supplyripple rejection (PSRR) and electrostatic discharge (ESD) protection,with high input impedance and low bias current.

FIG. 6 is a schematic block diagram of an embodiment of a pulsemodulator circuit in accordance with the present invention. This diagramshows a pulse modulator formed by output digital-to-analog converter(DAC) (1) and integrator resistor (R1) and capacitor (C1), feeds theanalog-to-digital converter (ADC) (2) input node on the 1 bit comparatordirectly at unity gain and then feed the output filter (EMI Filter) andsensor element (To Sensor Row/Column). This allows the modulator tofollow the second comparator input (3) while at the same time generatingthe internal digital representation of the signal (flip-flop output)required for following including any phase or amplitude shifts due tocircuit non-linearity or changes to the impedance of the sensor element.

The pulse modulator, formed by output DAC and integrator capacitor, mayfeed the ADC (input node on the 1 bit comparator) indirectly through afeedback impedance network and then feed the output filter and sensorelement. This allows the modulator to follow the second comparator inputwhile at the same time generating the internal digital representation ofthe signal required for following including any phase or amplitudeshifts. This feedback impedance network in combination with the filterand sensor impedance networks may be used and configured to set theanalog integrator and associated internal digital signal gain to agreater than unity. Further, the networks may be set to control thegains at different frequencies.

In addition, this disclosure also presents an Analog Front End (AFE)channel driver that acts as a channel driver to output signals andproduce an analog error output with gain set by feedback impedancecontrol. In addition, the impedance control also operates as impedancecontrol to the channel output signal properties. For variousapplications and as desired by design, sigma-delta (SD) analog todigital converters (ADC) may be a preferred digitization method whencoupled to the disclosed AFE for the digitization and output ofcontinuous measurements due to various benefits provided therebyincluding the SD's enhanced resolution and noise shaping properties. Inaddition, the analog error signal may also be further processed by aclassical ADC (FLASH, SAR, Integrating, etc.) to digitize the outputsignal properties.

FIG. 7 is a schematic block diagram of an embodiment of an Analog FrontEnd (AFE) channel driver circuit in accordance with the presentinvention. This diagram shows an AFE channel driver conversion system720, with an analog to digital conversion (ADC) module 702-1 (which mayalternatively be implemented as an SD module 702) coupled to the outputof an AFE channel driver circuit in accordance with various embodiments.The AFE channel driver circuit includes DAC module 700 that includes adifferential module 701 coupled to an ADC module 702, where thedifferential module 701 includes a differential amplifier and isconfigured to receive a signal reference (SIG (ref)) at one input. TheAFE channel driver circuit further includes a driver module 703 thatforms an outer loop feedback from the output of the differential module701 at an analog output node 707.

The driver module 703 may be configured as a voltage to current circuitand further configured to provide a variable power output capability viaan impedance setting control to a channel input/output (IO) node 704 todrive an analog signal at a desired current to a load 705. The drivermodule 703 receives an analog error signal from the differential module701 and converts the voltage error signal into an output current which,when reconstructed on load 705, forms an analog format substantiallysimilar to SIG (ref). This reconstructed signal is a virtualized versionof the SIG (ref) signal and referred to hereafter as SIG (virt). Thus,the AFE channel driver circuit has an analog I/O at the channel I/O node704 and an analog error output at node 707. In various embodiments, theanalog error signal at node 707 may pass through a filter 710 performingthe function of anti-aliasing or pass band limiting before coupling tothe ADC module 702. In operation, the ADC module 702 performs ananalog-to-digital conversion of the analog error signal created by theAFE channel driver circuit from the difference between the SIG (ref) andthe SIG (virt) signals.

The channel I/O node 704 is a node coupled to the driver module 703, aninput of the differential module 701, and the load 705. The load 705 canbe an analog device, such as any device or circuit capable of receivingand/or transmitting an analog signal to the AFE channel driver circuit,or an impedance network where changes to the network impedance are to bemeasured. For example, the analog device may be a touchscreen, which isan impedance network typically formed of resistances and capacitances,where an analog signal of typically less than 7 Mhz is driven to thetouch screen and a returning analog signal or change to the drivensignal can indicate whether a touch event has occurred. An externallyinjected signal may also be received in normal operation, such as a 500kHz signal present on the tip of a floating electrostatic pen. The AFEchannel driver circuit can also be used in applications with zeroresistance sensors (wires), inductors, capacitors, or resistiveelements, high frequency (HF) sensing using channel driver frequencygreater than 7 megahertz (MHz) for the transmission and reception of HFsignal, or as a form of network analyzer where pulses or signals ofdifferent frequencies can be used to quantify an unknown externalimpedance network coupled as a load 705.

The signal present at the channel I/O node 704 may be referred to as achannel driving signal. This signal is driven by the system 720 and actsas a virtual version of SIG (ref). In various embodiments, the channeldriving signal includes the analog output signal SIG (virt) generated bythe driver module 703 onto the load 705. Any signal sourced from theload 705 will be zeroed as a signal into a virtual ground but willbecome present as an inverted part of the spectrum of the analog signalerror at node 707.

In various embodiments, the differential amplifier circuit in thedifferential module 701 has a first input port coupled to the channelI/O node 704 and a second input node receiving the reference signal SIG(ref). SIG (ref) is a reference signal desired to be output to the load705 after being processed by the AFE channel driver circuit. Thedifferential module 701 compares and amplifies the difference betweenSIG (ref) and the SIG (virt) generating an analog error signal at node707, which is sent to the input of the driver module 703. The analogerror signal from the differential module 701 is also coupled to theinput of the ADC module 702.

The differential module 701 of the previous diagram may be implementedin a variety of embodiments based on the desiredperformance/attributes/characteristics required by the AFE channeldriver circuit.

In an example of operation and implementation, a channel driver circuitincludes a differential module (e.g., such as differential module 701 ofDAC module 700) and a driver module (e.g., such as driver module 703 ofDAC module 700).

The differential module is configured to receive a reference signal. Thedifferential module is also configured to receive, via a single node ofa load, a channel driving signal that is provided to the load at thesingle node. The differential module is also configured to generate ananalog error signal that is based on the channel driving signal and thereference signal. Note that the channel driving signal is based on anelectrical characteristic of the load.

The driver module is coupled to the differential module and configuredto generate the channel driving signal based on the analog error signalor a digital error signal corresponding to the analog error signal. Thedriver module is also configured to transmit the channel driving signalvia the single node to the load. Note that the channel driver circuit isconfigured simultaneously to transmit the channel driving signal to theload at the single node and to sense the channel driving signal at thesingle node.

In some variant embodiments, the channel driver circuit also includes asigma-delta module that is coupled to the differential module andconfigured to receive the analog error signal. Note that such asigma-delta module is implemented as an ADC in some examples. Thesigma-delta module is configured to process the analog error signal togenerate the digital error signal corresponding to the analog errorsignal. Also, the sigma-delta module is configured to transmit thedigital error signal corresponding to the analog error signal to acomputing device and/or processing circuitry to be processed inaccordance with interpreting the digital error signal.

In some examples, the differential module includes a differentialamplifier having a first input port configured to receive the channeldriving signal, a second input port configured to receive the referencesignal, and an output port configured to output the analog error signal.Also, the sigma-delta module includes an analog to digital converter(ADC) configured to process the analog error signal to generate thedigital error signal corresponding to the analog error signal. Inaddition, the driver module includes a digital to analog converter (DAC)configured to generate the channel driving signal based on the digitalerror signal corresponding to the analog error signal.

In addition, in some other examples, the sigma-delta module includes acomparator configured to receive the analog error signal and to processthe analog error signal to generate the digital error signalcorresponding to the analog error signal. Also, the sigma-delta moduleincludes a flip-flop circuit configured to store the digital errorsignal at least temporarily before transmitting the digital error signalcorresponding to the analog error signal to the computing device and/orthe processing circuitry to be processed in accordance with interpretingthe digital error signal.

In some examples, the channel driver circuit also includes a filterconfigured to process the analog error signal in accordance withanti-aliasing filtering and/or pass band limiting to generate a filtersignal. In addition, the channel driver circuit includes an analog todigital converter (ADC) configured to process the analog error signal togenerate the digital error signal corresponding to the analog errorsignal. The ADC is also configured to transmit the digital error signalcorresponding to the analog error signal to a computing device and/orprocessing circuitry to be processed in accordance with interpreting thedigital error signal corresponding to the analog error signal.

In addition, in some examples, the differential module includes adifferential amplifier having a first input port configured to receivethe channel driving signal, a second input port configured to receivethe reference signal via a resistor, and an output port that is coupledto the second input port via another resistor and/or a capacitor and isconfigured to output the analog error signal. Note that the analog errorsignal is output from the differential amplifier as a single-endedanalog error signal or a differential analog error signal.

Also, in some examples, the driver module includes a voltage to currentconverter circuitry configured to generate the channel driving signalbased on the analog error signal or the digital error signalcorresponding to the analog error signal.

Note that the load may be of any of a variety of types including any oneor more of an electrode of a touchscreen, a sensor, a transducer, adevice, an integrated circuit, circuitry, a computer, a tablet, a smartphone, an appliance, or a motor.

FIGS. 8A-8C illustrate examples of possible embodiments of adifferential module. Each of the embodiments shown in FIGS. 2A-2Cillustrate various implementations of a differential module including arespective differential amplifier configured to receive a first inputsignal SIG (ref) at a first input port and a second input signal SIG(virt) at a second input port, and generate an analog error signal atoutput.

FIG. 8A is a schematic block diagram of another embodiment of adifferential module in accordance with the present invention. Thisdiagram illustrates the differential module 801 generating a singleended analog error signal at the output 207. Differential amplifier 801a is configured to receive a first input signal SIG (ref) at a firstinput port 803 and a second input signal SIG (virt) at a second inputport 804, and generate an analog error signal at output 807 (e.g., asingle-ended analog error signal).

FIG. 8B is a schematic block diagram of another embodiment of adifferential module in accordance with the present invention. Thisdiagram illustrates the differential amplifier 801 further including acapacitor 805 acting as an integrator and coupled between the output 807and the second input port 803. Differential amplifier 801-1 a isconfigured to receive a first input signal SIG (ref) at a first inputport 803-1 and a second input signal SIG (virt) at a second input port804-1, and generate an analog error signal at output 807-1 (e.g., asingle-ended analog error signal).

FIG. 8C is a schematic block diagram of another embodiment of adifferential module in accordance with the present invention.Differential amplifier 801-2 a is configured to receive a first inputsignal SIG (ref) at a first input port 803-2 and a second input signalSIG (virt) at a second input port 804-2, and generate an analog errorsignal at output 807-2 (e.g., a single-ended analog error signal or adifferential analog error signal).

In the embodiments illustrated in FIGS. 8A and 8C, the negative terminalof the differential amplifier 801 can be configured to receive SIG (ref)and the positive terminal of the differential amplifier 810 can beconfigured to receive the channel driving signal SIG (virt). Conversely,as shown in FIG. 8B the negative terminal of the differential amplifier801 can be configured to receive the channel driving signal SIG (ref)and the positive terminal of the differential amplifier 801 can beconfigured to receive SIG (ref), where correcting inversion can beaccomplished in a driver module by inverting the output current. Thedifferential module may include one or more inverters to invert varioussignals as needed or desired in a particular implementation. In someexamples, a differential amplifier may also be implemented include acombination of circuit functions as described herein.

FIG. 9A is a schematic block diagram of another embodiment of a drivermodule (e.g., which may be implemented as a DAC) in accordance with thepresent invention. This diagram includes a driver module 903 thatinclude a current driver such as a voltage-to-current (V/I) converter901. The V/I converter 901 converts a voltage to a current in accordancewith a settable output impedance 906. In some examples, this isperformed during a start-up of a AFE channel driver system. The V/Iconverter 901 receives an analog error voltage signal at node 907 fromthe difference module output, and generates the SIG (virt) signalthrough negative feedback and gain of the system at the channel I/O node904, which connects to the load 905.

FIG. 9B is a schematic block diagram of another embodiment of a drivermodule (e.g., which may be implemented as a DAC) in accordance with thepresent invention. In some examples, a driver module 903-1 isimplemented to include a low pass filter (LPF) 920-1 at the output andcoupled to the channel I/O node 904-1, as shown in FIG. 9B. The V/Iconverter 901-1 receives an analog error signal and outputs a currentwith controllable impedance setting 906-1. Then, the LPF 920-1 convertsthe current back into a voltage signal which is delivered to the channelI/O node 904-1.

Functionally, the driver module 903 or 903-1 is configured to receivethe analog error signal from a differential module and pushes out acurrent that is reconstructed on the output (e.g., optionally from LPF920-1) or delivered directly to the channel I/O node 904 or 904-1 andreconstructed on the load 905 or 905-1. The feedback loop formed by thedriver module 903 or 903-1 903 forces the reconstructed voltage SIG(virt) to be substantially similar to the reference signal SIG (ref).Further, the V/I converter 901 or 901-1 is configured to generate achannel driving signal with a low virtual output impedance while stillmeasuring changes to the external signals with high gain and anequivalent high input impedance. For example, the channel driving signalSIG (virt) may have a virtual output impedance of 50 ohms (Ω) but theeffective input impedance of the signals as seen by an ADC module may be50,000Ω.

FIG. 10 is a schematic block diagram of an embodiment 1000 of an AFEchannel driver circuit coupled to a 1^(st) order sigma-delta (SD) modulein accordance with the present invention. Note that an ADC module suchas described herein may be implemented in a variety of ways includingusing analog to digital or sigma-delta modulation techniques forconversion of the analog error signal to a digital form. This diagramillustrates an AFE channel driver circuit coupled to a SD module 1010(e.g., which may be implemented as an ADC, ADC module, ADC circuitry,etc.) included of a 1^(nd) order sigma-delta modulator circuit.

This diagram includes DAC module 1000 that includes a differentialmodule 1021 coupled to SD module 1010 via a filter 1022, where thedifferential module 1001 includes a differential amplifier and isconfigured to receive a signal reference (SIG (ref)) at one input. TheDAC module 1020 includes a driver module 1023 that forms an outer loopfeedback from the output of the differential module 1021 at an analogoutput node 1027.

The driver module 1023 may be configured as a voltage to current circuitand further configured to provide a variable power output capability viaan impedance setting control to a channel input/output (IO) node 1004 todrive an analog signal at a desired current to a load 1095. The drivermodule 1003 receives an analog error signal from the differential module1001 and converts the voltage error signal into an output current which,when reconstructed on load 1095, forms an analog format substantiallysimilar to SIG (ref). This reconstructed signal is a virtualized versionof the SIG (ref) signal and referred to hereafter as SIG (virt). Thus,an analog I/O is provided at the channel I/O node 1004 and an analogerror output at node 1027. In various embodiments, the analog errorsignal at node 1027 may pass through the filter 1022 performing thefunction of anti-aliasing or pass band limiting before coupling to theSD module 1010. In operation, the SD module 1010 performs ananalog-to-digital conversion of the analog error signal created by theDAC module 1020 from the difference between the SIG (ref) and the SIG(virt) signals.

The channel I/O node 1004 is a node coupled to the driver module 1023,an input of the differential module 1021, and the load 1095. The load1095 can be an analog device, such as any device or circuit capable ofreceiving and/or transmitting an analog signal to the AFE channel drivercircuit, or an impedance network where changes to the network impedanceare to be measured.

The SD module 1010 includes an differential amplifier 1004, a capacitorC, a comparator 1001, a flip-flop circuit 1002, and a switch 1006. Thecapacitor C is an integrator coupled between an input and the output ofthe differential amplifier 1004. Further, the differential amplifier1004 provides a modulated analog error signal to the comparator 1001.The comparator 1001 and flip-flop circuit 1002 forms a 1-bit ADC withlatch as discussed above, with the flip-flop circuit 1002 storing the1-bit output from the comparator 1001. The 1-bit output forms a digitalsignal as an output signal, which also controls the switch 1006. Thecomparator 1001 compares the modulated error signal of the differentialamplifier 1004 and a reference signal to generate a digital errorsignal. If the analog error signal has increased in comparison to areference signal (e.g., shown as signal ground in FIG. 10), thecomparator 1001 generates a one (“1”). If the analog error signal hasdecreased, the comparator 1001 generates a zero (“0”). As such, the SDADC transmits the changes in, or the gradient of, the analog errorsignal. The flip-flop circuit 1002 stores the 1-bit output from thecomparator 1001. The 1-bit output forms a digital shaped noise spectrumwaveform as an output signal, which also controls the switch 1006. Theswitch (a feedback DAC) controls whether the high or low referencevoltage is connected to the second input of the differential amplifier1004. The switch 1006 is connected to the high reference voltage whenthe flip-flop circuit 1002 has a one (“1”) value and is connected to thelow reference voltage when the flip-flop circuit 1002 has a zero (“0”)value, or vice versa. The high or low level is subtracted from theincoming signal to the differential amplifier 1004 from the differentialmodule 101 and the difference is integrated on capacitor C thus thesigma-delta module tracks the average error and converts the incomingsignal into a digital pulse stream. Moreover, in various embodiments,the SD module 1010 can be of different architectures such assigma-delta, successive approximation, integrating, flash, etc.

FIG. 11 is a schematic block diagram of an embodiment of an AFE channeldriver circuit with DSP, computing system (e.g., one or more computingdevices and/or processing circuitry), and multi-channel load interactionin accordance with the present invention. The AFE channel driver systemmay have multiple AFE channel driver circuits (0, . . . , n) as shown inFIG. 11 with AFE channel driver circuits 1100 through 1116 (e.g., withAFE channel driver circuit 1116 depicting (0 to n) channels). Each AFEchannel driver circuit 1100 through 1116, when used as a systeminterface, may be implemented to connect to a LOAD Z Network 1105element, such as a touchscreen system.

In FIG. 11, an AFE channel driver circuit, for example AFE channeldriver circuit 1100, includes a differential module 1101 coupled to adriver module 1103. The differential module 1101 is configured toreceive a reference signal SIG (ref) at a first input and a signal SIG(virt) at a second input. The driver module 1103 forms a feedbackchannel from the output at node 1107 of the differential module 1101 tothe second input of the differential module 1101. The driver module 1103and the second input of the differential module 1101 are also coupled toa load 1105 impedance network, such as a touch screen. The AFE channeldriver circuit 1100 may further include typical functions in support ofanalog and digital circuits such as band pass references, power voltageregulators, etc.

In addition, in various embodiments, the AFE channel driver circuit 1100may include a level shifting (LS) circuit 1111, an anti-aliasing (AA)filter 1110, a sample and hold (S&H) circuit 1112, or a combinationthereof. The AA filter 1110 may be located between the output of thedifferential module 1101 and a coupled ADC 1102 to prevent aliasing ifdesired. The LS circuit 1111 may be located between the output of thedifferential module 1101 and a coupled ADC 1102. The LS circuit 1111 canbe used in embodiments where the external system ground driven by an AFEChannel Analog System differs from the external ground driven by an AFEChannel Digital System in order to transition the analog signal betweenthe two systems. For example, the analog system may require the AFE todrive a +/−1V signal with a ground reference of −2V.

Typically, an S&H circuit is built into the ADC 1102. However, it can bebeneficial to locate the S&H circuit 1112 between the output of thedifferential module 1101 and a coupled ADC 1102 in a “scanned system” orsystem using less than one ADC per channel to quickly convert all thechannels in a system. Such a system is illustrated by the multiple AFEchannel driver circuits 1100, 1116 and a Mux 1113 in FIG. 11. Tomaintain the concurrent modality properties of the multiple AFE channeldriver circuits 1100, 1116, analog channel signals can be sampledsimultaneously, where the sample value is held while the multiplechannels are read by an ADC 1102. Common mode noise may be subtracted inthe digital realm since all the samples are taken at one instant.

In various embodiments, the AFE channel driver circuit 1100 may furtherinclude a range detection circuit 1140 and a control block 1130. Therange detection circuit 1140 is coupled to the differential module 1101at output node 1107, and provides a signal if the amplitude of theanalog error signal is greater than the input range of the ADC to thecontrol block 1130. The control block 1130 sets the impedance of thedriver module 1103 in a digitally controlled or automated manner, so asto prevent signal saturation (clipping) at the ADC module 1102. Thecontrol block 1130 can be configured for testing, power control,clocking, gain/impedance setting, out of range detection, or othercontrol or reporting function coupled to a processing or state machineshown here as DSP block 1150.

The output of the AFE channel driver circuit 1100 may be coupled to amultiplexer circuit (Mux) 1113, which is coupled to an ADC module 1102.In some examples, the ADC module 1102 is implementation as a sigma-deltatype similar to the analog to digital converter such as with referenceto FIG. 10, or alternatively, as any other type of ADC such as FLASH,SAR, or any means of converting or digitizing the analog signal into adigital format.

Certain prior art touch systems typically employ S&H and MUX circuits onan input side of the system, where the Mux system causes added noise andloss of signal due to the internal switch transistors inherentcapacitive coupling to the power and ground and switch resistance.However, LS circuit 1111, AA filter 1110, S&H 1112, and Mux 1113 may beused with much less impact to system noise levels when implemented afterthe differential module 1101 of the AFE channel driver circuit 1100.

FIG. 12 is a schematic block diagram of another embodiment of an AFEchannel driver circuit in accordance with the present invention. Inaddition to the detailed embodiments described above, various other AFEcircuit configurations may be implemented in alternative embodiments asmay be desired. For example, this diagram shows a simplified diagram ofa single ended AFE channel driver showing the main elements V2I 1201 andDifference Amplifier 1203, with current driving the load (e.g., achannel load touch screen panel (TSP) 1205) through node 1204, and ADC1202.

FIG. 13 is a schematic block diagram of another embodiment of an AFEchannel driver circuit in accordance with the present invention. Thisdiagram provides an alternate AFE implementation that provides a way tomodulate a TSP load 1305 with a V/I converter 1301 and differenceamplifier 1303 and receive the capacitive change in the TSP 1305 via acurrent sensing technique. The sensed current is fed to the ADC 1310,and the ADC process the sensed current and provides a digitizedmeasurement of the sensed current. The V/I converter 1301 includes asimple current sink 1330 and transistor 1340. Current may be sourced orsunk with some level of current and impedance control with control 1320adjusting the strength of the current flow.

FIG. 14 is a schematic block diagram of embodiment of an AFE channeldriver circuit with voltage level translation in accordance with thepresent invention. This diagram provides a level translation circuit maybe used to correct differences in the sensed voltage between twodiffering ground reference circuits. The channel impedance TSP 1405 isdriven by the AFE, primarily composed of a difference amplifier 1403 anda V2I 1401. The AFE ground VCOM 1430 can be set above or below thesystem ground 1435. The Voltage Level Translator 1410 is the leveltranslation circuit and contains circuitry to send the sensed voltage tothe ADC 1402 for digitization and further processing in the digitalprocessor 1420. A first method for correcting differences is to ACcouple the differential sensed signal. As VCOM moves up and downrelative to the system ground, the voltage difference between VCOM andthe System ground is stored in AC coupling caps. The sensed voltageremains unchanged between the differential signal. Therefore, there isno loss of information. A second method for correcting differences is toplace a pair of resistors between the AFE and the ADC. The resistorswill carry both the common mode current and differential current. Thedifferential current contains the information, while the common modecurrent reflects the voltage difference between VCOM and the systemground. No information is lost in the differential current as VCOM movesrelative to the system ground.

FIG. 15 is a schematic block diagram of embodiment of an AFE channeldriver circuit operating with a low power triangle wave signal inaccordance with the present invention. In this diagram, an AFE systemincludes a differential output circuit 1503 performing the additionalfunctions of a level shifter and attenuator, and a V2I feedback circuit1501 measuring the analog error of a signal driven onto the TSP 1505 viaconnection node 1504. The connection node 1504 is also coupled to thesecond input of the differential output circuit 1503 and substantiallysimilar to the triangular signal 1530 coupled to the first input of thedifferential output circuit 1503, which may be produced via a simple lowpower analog signal generation technique. The triangular waveformreference signal 1530 can be as simple as a current sourcecharging/discharging a capacitor using an input square wave controllingthe switching of a current source to generate a triangular waveform. Theuse of a triangular waveform 1530 also reduces the slewing of the erroramplifier in the difference module 1503 and therefore results in lowerpower consumption. Further, two or more triangular wave forms may beadded in the analog domain to generate a multi-tone reference signal.

The use of triangular waveforms instead of arbitrary signals tocompletely remove the sigma-delta modulator (SDM) driver with theassociated quantization noise may help improve the system noise floor. ASDM modulator may be used to create AFE reference signals (SIG (ref))but can add quantization noise to the system and require digitalprocessing and filtering to remove the shaped noise both requiring extrapower dissipation in the system. Further, the digital system may be usedto generate square waves (50% duty cycle) with different frequencies.These square waves will be converted to triangular waveforms in theanalog domain. For example, by a square wave controlling two currentsources to charge/discharge a capacitor. In various embodiments, using a50% duty cycle square wave eliminates the 2nd harmonic. The 3rd harmonicwill be out of the signal band and may be filtered if necessary. Inaddition, the triangular waveform can be made very stable in anapplication-specific integrated circuit (ASIC) design. In variousembodiments, the differential analog error signal output from thedifferential output circuit 1503 is coupled to a differentialanti-aliasing filter 1510, such that the high frequency components areremoved before the differential signal goes to the input of adifferential sigma-delta ADC 1502. The output of the differentialsigma-delta ADC 1503 is a digitally modulated shaped noise data stream1535.

In accordance with various embodiments, the AFE channel driver circuitmay be manufactured on an ASIC separately or as part of a completesystem. A system of AFE with or without back end ADC may be used as aseparate component connected to other ASIC systems or FPGA systems fordigital back end processing and control.

With respect to the various embodiments described above, an AFE channeldriver circuit has the ability, and by default operates in a state of“concurrent modality” such as providing signals at one or morefrequencies to an analog I/O, monitoring the response of the drivensignals to modification of the channel's impedance characteristics, andsimultaneously receiving one or more externally generated signalfrequencies coupled into the channel. In various embodiments, the AFEchannel driver circuit operates with concurrent modality by driving alow impedance virtualized version of the first frequencies to the loadin a first mode, simultaneously operating to sense said virtual firstfrequencies properties and change due to impedance variation in the loadin a second mode, and simultaneously sensing one or more secondfrequencies injected into the load different from the first frequenciesin a third mode. Further, in a touchscreen operation, one or more AFEchannel driver circuit are configured for parallel communicatingtransmit/receive signals for mutual capacitance operation with one ormore rows or columns transmitting (using at least one frequency perline) continuously and one or more rows or columns receivingcontinuously.

The AFE channel driver circuit may operate in a continuous manner or maybe dropped into different low power states to reduce analog or digitalpower. Reduction of sampling clocks, deactivation of channels, reductionof output voltage or specific tones are but a few possible options.

Note that an AFE channel driver circuit, such as an AFE channel drivercircuit or system such as with reference to FIG. 5 or any other diagramsherein or their equivalents, can be implemented using an ASIC ordiscrete components. For example, FPGA may be used for the digitalprocessing of the AFE data stream after analog to digital conversion. Inaccordance with various embodiments, an AFE channel driver circuit iscapable of very fast signal data transmission with simultaneousmeasurement of the impedance characteristics of the external loadnetwork.

In various embodiments, an AFE channel driver circuits may include afeedback impedance network, I/O impedance networks, resistivecomponents, with variable or switched capacitor current shuttles withcontrollable frequency and duty cycle. The variable impedance of thedriver module allows changes to gain (inverting and non-inverting gain)and drive impedance. Further, a switched power supply (with frequencyand duty cycle control) or switched capacitor charge pump may be coupledto the V/I on the feedback loop such that high voltage can be used toincrease voltage overhead necessary due to gain or to increase theoutput signal driven onto the analog device. In some embodiments, therails of the differential amplifiers, comparator, and switches will alsohave high voltage rails. The SIG (ref) filter (e.g., LPF 1114 of FIG.11) can be a filter of low to high order as required to remove generatornoise. In various embodiments, the differential module can be replacedwith a differential amplifier having good power supply ripple rejection(PSRR) and electrostatic discharge (ESD) protection, with high inputimpedance and low bias current.

FIG. 16 is a schematic block diagram of an embodiment of a method 1600for execution by one or more devices in accordance with the presentinvention. The method 1600 operates by operating a differential modulein step 1610 by receiving a reference signal. The method 1600 alsooperates by operating the differential module in step 1620 by receiving,via a single node of a load, a channel driving signal that is providedto the load at the single node. The method 1600 also operates byoperating the differential module in step 1630 by generating an analogerror signal that is based on the channel driving signal and thereference signal. Note that the channel driving signal is based on anelectrical characteristic of the load.

The method 1600 operates by operating a driver module in step 1640 byoperating a driver module that is coupled to the differential module bygenerating the channel driving signal based on the analog error signalor a digital error signal corresponding to the analog error signal. Themethod 1600 also operates by operating the driver module in step 1650 bytransmitting the channel driving signal via the single node to the loadand also operating the channel driver circuit simultaneously fortransmitting the channel driving signal to the load at the single nodeand for sensing the channel driving signal at the single node.

FIG. 17 is a schematic block diagram of another embodiment of a method1700 for execution by one or more devices in accordance with the presentinvention. The method 1700 operates by operating a differential modulein step 1710 by receiving a reference signal. The method 1700 alsooperates by operating the differential module in step 1720 by receiving,via a single node of a load, a channel driving signal that is providedto the load at the single node. The method 1700 also operates byoperating the differential module in step 1730 by generating an analogerror signal that is based on the channel driving signal and thereference signal. Note that the channel driving signal is based on anelectrical characteristic of the load.

The method 1700 operates by operating a driver module in step 1740 byoperating a driver module that is coupled to the differential module bygenerating the channel driving signal based on a digital error signalcorresponding to the analog error signal. The method 1700 also operatesby operating the driver module in step 1750 by transmitting the channeldriving signal via the single node to the load and also operating thechannel driver circuit simultaneously for transmitting the channeldriving signal to the load at the single node and for sensing thechannel driving signal at the single node.

The method 1700 operates by operating a sigma-delta module coupled tothe differential module in step 1760 by receiving the analog errorsignal. The method 1700 also operates by operating the sigma-deltamodule in step 1770 by processing the analog error signal to generatethe digital error signal corresponding to the analog error signal. Themethod 1700 also operates by operating the sigma-delta module in step1780 by transmitting the digital error signal corresponding to theanalog error signal to a computing device and/or processing circuitry tobe processed in accordance with interpreting the digital error signal.

In addition, note that the one or more signals provided from any channeldriver circuit as described herein, or their equivalents, may be of anyof a variety of types. For example, such a signal may be based onencoding of one or more bits to generate one or more coded bits used togenerate modulation data (or generally, data). For example, a device isconfigured to perform forward error correction (FEC) and/or errorchecking and correction (ECC) code of one or more bits to generate oneor more coded bits. Examples of FEC and/or ECC may include turbo code,convolutional code, turbo trellis coded modulation (TTCM), low densityparity check (LDPC) code, Reed-Solomon (RS) code, BCH (Bose andRay-Chaudhuri, and Hocquenghem) code, binary convolutional code (BCC),Cyclic Redundancy Check (CRC), and/or any other type of ECC and/or FECcode and/or combination thereof, etc. Note that more than one type ofECC and/or FEC code may be used in any of various implementationsincluding concatenation (e.g., first ECC and/or FEC code followed bysecond ECC and/or FEC code, etc. such as based on an inner code/outercode architecture, etc.), parallel architecture (e.g., such that firstECC and/or FEC code operates on first bits while second ECC and/or FECcode operates on second bits, etc.), and/or any combination thereof.

Also, the one or more coded bits may then undergo modulation or symbolmapping to generate modulation symbols (e.g., the modulation symbols mayinclude data intended for one or more recipient devices, components,elements, etc.). Note that such modulation symbols may be generatedusing any of various types of modulation coding techniques. Examples ofsuch modulation coding techniques may include binary phase shift keying(BPSK), quadrature phase shift keying (QPSK), 8-phase shift keying(PSK), 16 quadrature amplitude modulation (QAM), 32 amplitude and phaseshift keying (APSK), etc., uncoded modulation, and/or any other desiredtypes of modulation including higher ordered modulations that mayinclude even greater number of constellation points (e.g., 1024 QAM,etc.).

In addition, note that a signal provided from any channel driver circuitas described herein, or their equivalents, may be of a unique frequencythat is different from signals provided from other any channel drivercircuits as described herein, or their equivalents. Also, a signalprovided from any channel driver circuit as described herein, or theirequivalents, may include multiple frequencies independently orsimultaneously. The frequency of the signal can be hopped on apre-arranged pattern. In some examples, a handshake is establishedbetween one or more any channel driver circuits as described herein, ortheir equivalents, and one or more processing module (e.g., one or morecontrollers) such that the one or more any channel driver circuit/s asdescribed herein, or their equivalents, is/are directed by the one ormore processing modules regarding which frequency or frequencies and/orwhich other one or more characteristics of the one or more signals touse at one or more respective times and/or in one or more particularsituations.

With respect to any signal that is driven and simultaneously detected byany channel driver circuit as described herein, or their equivalents,note that any additional signal that is coupled into a line, anelectrode, a touch sensor, a bus, a communication link, an electricalcoupling or connection, etc. associated with that channel driver circuitas described herein, or their equivalents, is also detectable. Forexample, any channel driver circuit as described herein, or theirequivalents, that is associated with such a line, an electrode, a touchsensor, a bus, a communication link, an electrical coupling orconnection, etc. is configured to detect any signal from one or moreother lines, electrodes, a touch sensors, a buses, a communicationlinks, electrical couplings or connections, etc. that get coupled intothat line, electrode, touch sensor, bus, communication link, electricalcoupling or connection, etc.

Note that the different respective signals that are driven andsimultaneously sensed by one or more any channel driver circuits asdescribed herein, or their equivalents, may be are differentiated fromone another. Appropriate filtering and processing can identify thevarious signals given their differentiation, orthogonality to oneanother, difference in frequency, etc. Other examples described hereinand their equivalents operate using any of a number of differentcharacteristics other than or in addition to frequency.

It is noted that terminologies as may be used herein such as bit stream,stream, signal sequence, etc. (or their equivalents) have been usedinterchangeably to describe digital information whose contentcorresponds to any of a number of desired types (e.g., data, video,speech, text, graphics, audio, etc. any of which may generally bereferred to as ‘data’).

As may be used herein, the terms “substantially” and “approximately”provide an industry-accepted tolerance for its corresponding term and/orrelativity between items. For some industries, an industry-acceptedtolerance is less than one percent and, for other industries, theindustry-accepted tolerance is 10 percent or more. Other examples ofindustry-accepted tolerance range from less than one percent to fiftypercent. Industry-accepted tolerances correspond to, but are not limitedto, component values, integrated circuit process variations, temperaturevariations, rise and fall times, thermal noise, dimensions, signalingerrors, dropped packets, temperatures, pressures, material compositions,and/or performance metrics. Within an industry, tolerance variances ofaccepted tolerances may be more or less than a percentage level (e.g.,dimension tolerance of less than +/−1%). Some relativity between itemsmay range from a difference of less than a percentage level to a fewpercent. Other relativity between items may range from a difference of afew percent to magnitude of differences.

As may also be used herein, the term(s) “configured to”, “operablycoupled to”, “coupled to”, and/or “coupling” includes direct couplingbetween items and/or indirect coupling between items via an interveningitem (e.g., an item includes, but is not limited to, a component, anelement, a circuit, and/or a module) where, for an example of indirectcoupling, the intervening item does not modify the information of asignal but may adjust its current level, voltage level, and/or powerlevel. As may further be used herein, inferred coupling (i.e., where oneelement is coupled to another element by inference) includes direct andindirect coupling between two items in the same manner as “coupled to”.

As may even further be used herein, the term “configured to”, “operableto”, “coupled to”, or “operably coupled to” indicates that an itemincludes one or more of power connections, input(s), output(s), etc., toperform, when activated, one or more its corresponding functions and mayfurther include inferred coupling to one or more other items. As maystill further be used herein, the term “associated with”, includesdirect and/or indirect coupling of separate items and/or one item beingembedded within another item.

As may be used herein, the term “compares favorably”, indicates that acomparison between two or more items, signals, etc., provides a desiredrelationship. For example, when the desired relationship is that signal1 has a greater magnitude than signal 2, a favorable comparison may beachieved when the magnitude of signal 1 is greater than that of signal 2or when the magnitude of signal 2 is less than that of signal 1. As maybe used herein, the term “compares unfavorably”, indicates that acomparison between two or more items, signals, etc., fails to providethe desired relationship.

As may be used herein, one or more claims may include, in a specificform of this generic form, the phrase “at least one of a, b, and c” orof this generic form “at least one of a, b, or c”, with more or lesselements than “a”, “b”, and “c”. In either phrasing, the phrases are tobe interpreted identically. In particular, “at least one of a, b, and c”is equivalent to “at least one of a, b, or c” and shall mean a, b,and/or c. As an example, it means: “a” only, “b” only, “c” only, “a” and“b”, “a” and “c”, “b” and “c”, and/or “a”, “b”, and “c”.

As may also be used herein, the terms “processing module”, “processingcircuit”, “processor”, “processing circuitry”, and/or “processing unit”may be a single processing device or a plurality of processing devices.Such a processing device may be a microprocessor, micro-controller,digital signal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on hard coding of thecircuitry and/or operational instructions. The processing module,module, processing circuit, processing circuitry, and/or processing unitmay be, or further include, memory and/or an integrated memory element,which may be a single memory device, a plurality of memory devices,and/or embedded circuitry of another processing module, module,processing circuit, processing circuitry, and/or processing unit. Such amemory device may be a read-only memory, random access memory, volatilememory, non-volatile memory, static memory, dynamic memory, flashmemory, cache memory, and/or any device that stores digital information.Note that if the processing module, module, processing circuit,processing circuitry, and/or processing unit includes more than oneprocessing device, the processing devices may be centrally located(e.g., directly coupled together via a wired and/or wireless busstructure) or may be distributedly located (e.g., cloud computing viaindirect coupling via a local area network and/or a wide area network).Further note that if the processing module, module, processing circuit,processing circuitry and/or processing unit implements one or more ofits functions via a state machine, analog circuitry, digital circuitry,and/or logic circuitry, the memory and/or memory element storing thecorresponding operational instructions may be embedded within, orexternal to, the circuitry comprising the state machine, analogcircuitry, digital circuitry, and/or logic circuitry. Still further notethat, the memory element may store, and the processing module, module,processing circuit, processing circuitry and/or processing unitexecutes, hard coded and/or operational instructions corresponding to atleast some of the steps and/or functions illustrated in one or more ofthe Figures. Such a memory device or memory element can be included inan article of manufacture.

One or more embodiments have been described above with the aid of methodsteps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claims. Further, the boundariesof these functional building blocks have been arbitrarily defined forconvenience of description. Alternate boundaries could be defined aslong as the certain significant functions are appropriately performed.Similarly, flow diagram blocks may also have been arbitrarily definedherein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence couldhave been defined otherwise and still perform the certain significantfunctionality. Such alternate definitions of both functional buildingblocks and flow diagram blocks and sequences are thus within the scopeand spirit of the claims. One of average skill in the art will alsorecognize that the functional building blocks, and other illustrativeblocks, modules and components herein, can be implemented as illustratedor by discrete components, application specific integrated circuits,processors executing appropriate software and the like or anycombination thereof.

In addition, a flow diagram may include a “start” and/or “continue”indication. The “start” and “continue” indications reflect that thesteps presented can optionally be incorporated in or otherwise used inconjunction with one or more other routines. In addition, a flow diagrammay include an “end” and/or “continue” indication. The “end” and/or“continue” indications reflect that the steps presented can end asdescribed and shown or optionally be incorporated in or otherwise usedin conjunction with one or more other routines. In this context, “start”indicates the beginning of the first step presented and may be precededby other activities not specifically shown. Further, the “continue”indication reflects that the steps presented may be performed multipletimes and/or may be succeeded by other activities not specificallyshown. Further, while a flow diagram indicates a particular ordering ofsteps, other orderings are likewise possible provided that theprinciples of causality are maintained.

The one or more embodiments are used herein to illustrate one or moreaspects, one or more features, one or more concepts, and/or one or moreexamples. A physical embodiment of an apparatus, an article ofmanufacture, a machine, and/or of a process may include one or more ofthe aspects, features, concepts, examples, etc. described with referenceto one or more of the embodiments discussed herein. Further, from figureto figure, the embodiments may incorporate the same or similarly namedfunctions, steps, modules, etc. that may use the same or differentreference numbers and, as such, the functions, steps, modules, etc. maybe the same or similar functions, steps, modules, etc. or differentones.

Unless specifically stated to the contra, signals to, from, and/orbetween elements in a figure of any of the figures presented herein maybe analog or digital, continuous time or discrete time, and single-endedor differential. For instance, if a signal path is shown as asingle-ended path, it also represents a differential signal path.Similarly, if a signal path is shown as a differential path, it alsorepresents a single-ended signal path. While one or more particulararchitectures are described herein, other architectures can likewise beimplemented that use one or more data buses not expressly shown, directconnectivity between elements, and/or indirect coupling between otherelements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of theembodiments. A module implements one or more functions via a device suchas a processor or other processing device or other hardware that mayinclude or operate in association with a memory that stores operationalinstructions. A module may operate independently and/or in conjunctionwith software and/or firmware. As also used herein, a module may containone or more sub-modules, each of which may be one or more modules.

As may further be used herein, a computer readable memory includes oneor more memory elements. A memory element may be a separate memorydevice, multiple memory devices, or a set of memory locations within amemory device. Such a memory device may be a read-only memory, randomaccess memory, volatile memory, non-volatile memory, static memory,dynamic memory, flash memory, cache memory, and/or any device thatstores digital information. The memory device may be in a form asolid-state memory, a hard drive memory, cloud memory, thumb drive,server memory, computing device memory, and/or other physical medium forstoring digital information.

While particular combinations of various functions and features of theone or more embodiments have been expressly described herein, othercombinations of these features and functions are likewise possible. Thepresent disclosure is not limited by the particular examples disclosedherein and expressly incorporates these other combinations.

What is claimed is:
 1. A channel driver circuit comprising: adifferential module configured to generate an analog error signal thatis based on a difference between a reference signal and an analog signalthat is received via a node of the channel driver circuit that couplesto an electrical load; a sigma-delta module coupled to the differentialmodule and configured to process the analog error signal to generate adigital error signal; and a driver module that is coupled to thedifferential module and configured to: generate the analog signal basedon the digital error signal including to vary power of the analog signalbased on change of the digital error signal; and provide the analogsignal via the node of the channel driver circuit that couples to theelectrical load.
 2. The channel driver circuit of claim 1, whereinchange of the digital error signal corresponds to at least one of anelectrical characteristic of the electrical load or a change of theelectrical characteristic of the electrical load.
 3. The channel drivercircuit of claim 1, wherein the differential module, the sigma-deltamodule, and the driver module are configured to operate cooperatively totransmit the analog signal and simultaneously to sense the analog signalincluding any change of the analog signal via the node of the channeldriver circuit.
 4. The channel driver circuit of claim 1, wherein: theanalog error signal is a single-ended analog error signal or adifferential analog error signal; and the digital error signal includesM bits, wherein M is a positive integer greater than or equal to
 1. 5.The channel driver circuit of claim 1, wherein the differential moduleis further configured to receive the reference signal via a third nodeof the channel driver circuit that couples to another circuit.
 6. Thechannel driver circuit of claim 1, wherein the driver module isimplemented as a voltage to current (V2I) converter circuit.
 7. Thechannel driver circuit of claim 1, wherein the driver module includes avoltage to current (V2I) converter circuit coupled to a low pass filter(LPF).
 8. The channel driver circuit of claim 1, wherein the analogerror signal is a single-ended analog error signal or a differentialanalog error signal.
 9. The channel driver circuit of claim 1, whereinthe differential module includes a differential amplifier having a firstinput port configured to receive the analog signal, a second input portconfigured to receive the reference signal, and an output portconfigured to output the analog error signal.
 10. The channel drivercircuit of claim 1, wherein the electrical load includes an electrode ofa touchscreen, a sensor, a transducer, a device, an integrated circuit,circuitry, a computer, a tablet, a smart phone, an appliance, or amotor.
 11. A channel driver circuit comprising: a differential moduleconfigured to generate an analog error signal that is based on adifference between a reference signal and an analog signal that isreceived via a node of the channel driver circuit that couples to anelectrical load; a sigma-delta module coupled to the differential moduleand configured to process the analog error signal to generate a digitalerror signal, wherein the digital error signal is also coupled from thesigma-delta module to at least one of a computing device or processingcircuitry to be interpreted by the at least one of the computing deviceor the processing circuitry; a digital low pass filter (LPF) coupled tothe sigma-delta module and configured to process the digital errorsignal to generate a filtered digital error signal; and a driver modulethat is coupled to the differential module and configured to: generatethe analog signal based on the filtered digital error signal includingto vary power of the analog signal based on change of the filtereddigital error signal; and provide the analog signal via the node of thechannel driver circuit that couples to the electrical load.
 12. Thechannel driver circuit of claim 11, wherein change of the digital errorsignal corresponds to at least one of an electrical characteristic ofthe electrical load or a change of the electrical characteristic of theelectrical load.
 13. The channel driver circuit of claim 11, wherein thedifferential module, the sigma-delta module, and the driver module areconfigured to operate cooperatively to transmit the analog signal andsimultaneously to sense the analog signal including any change of theanalog signal via the node of the channel driver circuit.
 14. Thechannel driver circuit of claim 11, wherein: the analog error signal isa single-ended analog error signal or a differential analog errorsignal; and the digital error signal includes M bits, wherein M is apositive integer greater than or equal to
 1. 15. The channel drivercircuit of claim 11, wherein the differential module is furtherconfigured to receive the reference signal via a third node of thechannel driver circuit that couples to another circuit.
 16. The channeldriver circuit of claim 11, wherein the driver module is implemented asa voltage to current (V2I) converter circuit.
 17. The channel drivercircuit of claim 11, wherein the driver module includes a voltage tocurrent (V2I) converter circuit coupled to a low pass filter (LPF). 18.The channel driver circuit of claim 11, wherein the analog error signalis a single-ended analog error signal or a differential analog errorsignal.
 19. The channel driver circuit of claim 11, wherein thedifferential module includes a differential amplifier having a firstinput port configured to receive the analog signal, a second input portconfigured to receive the reference signal, and an output portconfigured to output the analog error signal.
 20. The channel drivercircuit of claim 11, wherein the electrical load includes an electrodeof a touchscreen, a sensor, a transducer, a device, an integratedcircuit, circuitry, a computer, a tablet, a smart phone, an appliance,or a motor.